Conventionally, a passenger protection system includes a sensor for outputting a detection data corresponding to an amount of impact when an object collides with a vehicle, a passenger protection device for protecting a passenger of the vehicle from collision, and a ECU for controlling the passenger protection device. In the system, the ECU determines based on the detection data from the sensor whether it is necessary to protect the passenger from occurrence of the collision. When the ECU determines that it is necessary to protect the passenger from collision, the ECU controls the passenger protection device. This system is described in, for example, JP-A-2007-8392.
However, in the above case, bit fixation may occur at a specific bit in a memory medium in the ECU for storing the detection data received from the sensor. Thus, collision determination may be incorrect.
In view of the above difficulty, the present inventor has studied a system. Specifically, to reduce the possibility of failure of determination that it is necessary to protect the passenger from collision, as shown in FIG. 7, detection data 52 output from a sensor 51 is stored in two different portions 54, 55 in a ECU 53. Then, two data in the portions 54, 55 are compared with each other. When the two data are not the same, the system determines malfunction, and then, the system deletes the two data.
Thus, the system reduces the possibility of failure of determination. However, function of the passenger protection system for detecting collision to protect the passenger may be reduced.